Respiratory changes during defecation in patients with chronic respiratory failure.

Oxygen (O2) desaturation may occur in patients affected by respiratory diseases during daily activities, although most of these activities, e.g. walking, washing and cooking, can be avoided or eventually performed with an external aid. In this prospective study, the respiratory changes induced by the mandatory effort of defecation were assessed in patients with chronic respiratory insufficiency. Twenty-four consecutive patients with chronic respiratory failure due to obstructive or restrictive pulmonary disorders, showing a marked O2 desaturation during the 6-min walk test, were enrolled. Thirteen of them were already established on long-term O2 therapy (LTOT), while 11 were not. O2 saturation (Sa,O2), respiratory rate (RR), cardiac frequency (fC) and dyspnoea were measured at rest, and during and after defecation. Sa,O2 decreased significantly during defecation, while RR, fC and dyspnoea increased, both in the subgroup of patients without significant resting hypoxaemia and in the subgroup of patients receiving their usual resting flow of LTOT, as compared to resting values. In conclusion, the respiratory system of patients with chronic respiratory failure may be significantly strained by defecation.